Acrodermatitis enteropathica due to zinc deficiency is characterized by periorificial dermatitis, alopecia, and intractable diarrhea. Here we report a case of transient acrodermatitis enteropathica in a 2-month-old preterm infant, whose skin is erythematous, scaly, eczematous, with an eruption starting from the periorificial area. While her serum zinc level was normal at 118.2 ug/dL, the serum alkaline phosphatase level was low at 48 IU/L and the serum alkaline phosphatase level get increased concordant with clinical improvement after zinc supplementation. Hence, this case shows that the diagnosis of zinc deficiency can be aided with a low level of serum alkaline phoaphatase although serum zinc level is normal.